“I kept thinking, what would be the closest thing to a 100 miler that I can do at home?” Bitter told Runner’s World prior to the event. “The treadmill seemed like something different, and I think it’s fun to go for something more out in left that you’re not comfortable with.”

Already in racing shape, Bitter tailored his workouts to suit the needs of a fast treadmill workout. Even so, he didn’t spend too much time on the treadmill—his longest run on a machine was 30 miles, which he did two weeks ago.

But given his background, the physical prep was just as important as the mental.

“It’s a psychological thing,” he said. “When I do track events, I feel in control and my splits are even. On a treadmill, you set and forget, which is nice because you don’t have to worry, but you lose control a bit. You respond to the treadmill instead of the track responding to you.”

To counter this, Bitter planned to fluctuate his pace between just above and just below seven-minute pace throughout the race.

In addition to pace control, Bitter also spoke with athletes who had done similar projects to plan for the physical aches that can come from long-distance treadmill running.

“Biomechanics are very important, so you need some sort of variation to give your body something a little different over time,” Bitter said. “I spoke with another runner, and he recommended changing the incline every so often to stretch out the hips and hamstrings.”

The attempt started bright and early Saturday. Throughout the day, Bitter switched between two NordicTrack X22i Incline Trainers treadmills in his single-story Phoenix home every few hours to prevent the treadmills from auto shutting down.

While focused on his run, a cast of running celebrities, like Jamil Coury, Dean Karnazes, Courtney Dauwalter, Maggie Guterl, and Sally McRae, tuned in to entertain as Bitter ran. There was also an unexpected appearance during hour 10 by comedian Bert Kreischer, who ran seven miles on the treadmill before jumping on the stream.

“I ran at the pace he was running at, and it was a full-blown sprint for me,” Kreischer said on the feed.

Photo credit: Courtesy of Zach Bitter

Bitter also had support from Fight For the Forgotten, an anti-bullying nonprofit in the U.S. that also helps people in oppressed countries internationally through water, land, and food projects. Bitter has supported the organization since he got involved with it six months ago (you can donate to his cause here).

At the halfway point, Bitter was averaging a 7:03 pace, giving him a comfortable cushion ahead of Proctor’s pace from May 2019. He slowed down a bit for the next 10 miles before dropping a 5:42 for mile 62. He looked tired over the next few miles, and he took a slightly extended break at mile 87 to eat a bag of potato chips in the bathroom to lift his spirits—that was the only solid food he ate during the effort.

Once he hit mile 90, he found another gear to bring him into the finish, completing the 100 miles in 12:09:15, which broke the record by 21:21. His wife, Nicole Bitter, even made him a toilet paper finish line to cross.

“There were a few spots in there where physically you feel fine, but mentally you just want to get off that machine so badly,” Bitter said after the race. “It’s a beautiful machine, but 12 hours of anything is a lot.”

With this run in the books, Bitter is still in limbo, waiting for what the rest of the year holds for him. As he waits, he plans to devote time to planning for a potential cross-country record run in 2021.

“I’ve never been fascinated by [fastest known time] stuff, but when I got into the sport 10 years ago, I thought this was a project I’d like to do in my career,” Bitter said. “I think it would be a fun, new challenge like the treadmill, just a little different.”